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Property, Plant and Equipment - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Property, Plant and Equipment [Line Items]        
Impairment of oil and gas properties $ 1,439 $ 56 $ 2,243 $ 762
Unproved property leases [Member]
       
Property, Plant and Equipment [Line Items]        
Impairment of oil and gas properties $ 1,400 $ 100 $ 2,200 $ 800